Booster seats
Booster seat law by height and weight
Under ECE R44, group 2 covers 15 kg to 25 kg and group 3 covers 22 kg to 36 kg. Approved R129 boosters instead use the height range and any maximum weight printed on their label.
These rules apply in Great Britain.
Rules and figures checked on 10 September 2026.
The label decides which child fits
A high backed booster or booster cushion is legal only when it is approved, suitable for the child under its stated limits and fitted as the manufacturer instructs. Age estimates do not replace the label limits.
The booster requirement ends when the child reaches 135 cm or their 12th birthday, whichever occurs first. They must then wear the adult seat belt where one is fitted.
R44 groups overlap
The official weight table allows more than one seat type at some weights. Group 2 runs from 15 kg to 25 kg and group 3 from 22 kg to 36 kg, so the seat's own approval range remains decisive.
Common questions
- Is a booster seat a child restraint?
- Yes. GOV.UK includes high backed booster seats and booster cushions in the approved weight based child seat groups.
- Which R44 groups cover boosters?
- The GOV.UK table lists high backed boosters and booster cushions in group 2 at 15 kg to 25 kg and group 3 at 22 kg to 36 kg.
- When can a child use an adult seat belt?
- A child can use an adult seat belt from their 12th birthday or once they reach 135 cm tall, whichever happens first. The belt must be worn where one is fitted.
Related pages
- Child car seat law and seat checkerIn Great Britain, a child normally needs an approved child car seat until their 12th birthday or until they reach 135 cm, whichever happens first. The seat must match the child's height or weight and be fitted as its manufacturer directs.
- i-Size and R129 child car seatsGOV.UK identifies legal height based restraints by a capital E in a circle and R129 on the approval label. These seats are commonly called i-Size seats. They must remain rear facing until the child is over 15 months old.
- Rear facing child car seat lawA height based R129 seat must face the rear until the child is over 15 months old. A rear facing baby seat must never be placed in front of an active frontal airbag.
- Backless booster seat lawFrom 9 February 2017, manufacturers could introduce new backless booster models only for children at least 125 cm tall and at least 22 kg. Existing approved group 2 cushions were not withdrawn by that change.
Sources
Each legal threshold and exception above comes from the linked government guidance.